Ivermectin performance against equine strongylids: Efficacy, egg reappearance periods, and fecal egg counting method comparison.

The research focuses on assessing the efficacy of the drug Ivermectin against equine strongylids which are common parasites in horses. The study also compares two different methods of counting fecal egg counts, and investigates the prevalence of a specific parasite, Strongylus vulgaris, in Danish horses.

Overview of the Study

• The research concerns the performance of the drug Ivermectin against equine strongylids, parasites widespread in horses and responsible for severe health problems. The study arises from emerging resistance to common anthelmintic drugs, particularly in cyathostomin parasites.
• The study includes 299 horses from 30 different herds, selected by four collaborating veterinary practices in Denmark. The aim is to examine the efficacy of Ivermectin, the egg reappearance period (ERP), and to compare the techniques of fecal egg count.

Ivermectin Efficacy and ERP

• All horses with detectable eggs per gram of feces were treated with Ivermectin. The research used a faecal egg count reduction test (FECRT) to determine Ivermectin efficiency and evaluate the ERP.
• The ERP of Ivermectin was found to be at least 8 weeks in all instances, indicating no occurence of reduction. Also, the prevalence of Strongylus vulgaris, a parasite species, was around 2.7%-5.7% in the horse populations.
• Results overall showed that Ivermectin still had high efficiency. However, some isolated cases suggest potential reduced efficacy, necessitating further, future monitoring.

Comparison of Fecal Egg Count Techniques

• The research employed two distinct methods to count fecal eggs: a concentration McMaster technique and an artificial-intelligence-based automated system.
• The McMaster egg counts indicated inconclusive Ivermectin efficacy in two horse operations and full effectiveness in the rest, whereas the automated system suggested Ivermectin resistance in six operations and returned inconclusive findings for eight others.
• The two egg counting techniques generally gave concordant results. However, the automated system detected lower egg counts leading to lower efficacy estimates in certain populations.

Prevalence of Strongylus vulgaris

• The study determined the presence of Strongylus vulgaris in the horse population using coproculture and PCR testing.
• The prevalence of this parasite was found to be 2.7% and 5.7% with coproculture and PCR tests respectively. Additionally, all samples showed negative results at 8 and 24 weeks after treatment.
• Despite the high overall Ivermectin efficacy, the persistence of Strongylus vulgaris in Danish horses was confirmed.